Far Seer guide damage

[xerrol nanoha]

Increases the range and damage of an allied unit by 30% for 10 seconds.
30 second cooldown.
http://dow.wikia.com/wiki/Elite/Guide

Is it ranged damage only? Does it effect ability damage (i.e. plasma grenades)?
What then are the best squads or vehicles to cast guide on?

[Vapor]

It's melee damage too, and it does work on grenades, not sure about other abilities.

[Dark Riku]

Increases the range and damage of an allied unit by 30% for 10 seconds.
30 second cooldown.
http://dow.wikia.com/wiki/Elite/Guide

Is it ranged damage only? Does it effect ability damage (i.e. plasma grenades)?

Range and damage. Yes just like embolden increases a grenade's damage.

[Caeltos]

You can even use it on vehicles.

[Uncle Milty]

Guide boosts weapon damage.
So every weapon will be buffed.

Unlike i said at some other point prior to this, the ability "plasma grenade" does call a weapon and fires one shot. So grenades technically do not inflict ability damage but weapon damage (same goes for warlock destructor btw). There are only very few abilities for eldar that do not call a weapon, i.e. the psystorm from the farseer robe (so it does not get buffed with guide).

[FiSH]

Unlike i said at some other point prior to this, the ability "plasma grenade" does call a weapon and fires one shot.

Which is why smoke shells reduce grenade damage. By the way, am I the only one that thinks this makes no sense at all?
Example: it pisses me off when I chuck two grenades at a multi-las turret only to see catachans deploy a smoke shell and save it. (this happened in retail. the values have changed now, so not 100% if this happens in elite.)

[xerrol nanoha]

Range and damage. Yes just like embolden increases a grenade's damage.

How does Embolden and Guide stack (with regard to plasma grenade)?
is it (260 x 1.25) x 1.3 = 422.5
or is it 260 x (1.0 + .3 + .25) = 403

[Bahamut]

Range and damage. Yes just like embolden increases a grenade's damage.

How does Embolden and Guide stack (with regard to plasma grenade)?
is it (260 x 1.25) x 1.3 = 422.5
or is it 260 x (1.0 + .3 + .25) = 403

most probably the second, since both are temporary modifiers